Many radiotelephones employ retractable antennas, i.e., antennas which are extendable and retractable out of the radiotelephone housing. The retractable antennas are electrically connected to a signal processing circuit positioned on an internally disposed printed circuit board. In certain markets, it is desired that the antenna behave as a quarter wave resonator in both the extended and retracted position. Thus, in order to optimally operate, the antenna should be configured to provide the desired impedance to the signal processing circuit in both positions. Unfortunately, complicating such a configuration, a retractable antenna by its very nature has dynamic components, i.e., components which move or translate with respect to the housing and the printed circuit board, and as such does not generally have a single impedance value. Instead, the retractable antenna, if electrically contiguous, can generate largely different impedance values when in an extended versus a retracted position.
In the past, the antenna was configured to electrically separate two quarter wave components, one electrically connected in the retracted position and one electrically connected in the extended position. For example, as shown in FIG. 1, the antenna 10 includes a quarter wave helix 12 in the tip and a main rod or whip 14 sized to provide a quarter wave length resonance. The two electrical components were isolated by positioning a non-conductive plastic component 16 between the helix 12 and the rod 14. Unfortunately, the durability of this type of antenna can be problematic because the structure is easily broken during mechanical stress. As shown in the enlarged view of FIG. 1A, the antenna is prone to breakage at the non-conductive joint 18 between the whip and helix 12, 14. Also unfortunately, designs which enlarge the structure in an attempt to make the area more rigid, can make the antenna aesthetically undesirable to consumers. Further, designs which attempt to strengthen the configuration must generally do so in a way which provides the quarter wave resonance in both the extended and retracted position, a task that can involve additional circuit complexities.